1. Field of the Invention
This invention relates to a process and apparatus for cutting and trimming printed circuit board workpieces, particularly of multilayer printed circuit workpieces.
2. Description of the Prior Art
In the manufacture of such multilayer printed circuit boards, an outer layer is covered with synthetic resin interlayers and with circuit board inner layers built up in alternation in an operation in which the positions of the various layers are defined by means of suitable locating means, such as locating pins. The printed circuit board workpieces are subsequently compacted under the action of heat and pressure in an operation in which the synthetic resin is rendered flowable and flows outwardly in the plane of the respective layer beyond the contour of the workpiece and when the synthetic resin has been cooled and solidified it constitutes an undefined marginal portion, which varies in width. As printed circuit board workpieces are often cut in a size which exceeds the area which is subsequently utilized, the marginal portion formed by the synthetic resin which has been squeezed out may be confined between the surplus marginal portions of the oversize printed circuit board workpiece.
That marginal portions of the oversize printed circuit board workpiece and the marginal portion formed by the synthetic resin must be removed so that a printed circuit board having exactly the required size will be obtained. The trimmed multilayer board from which the marginal portions have been removed should be free of burrs and must be profiled at its edges so that the further processing will not result in defects caused by loose particles or sharp edges. In known processes this is accomplished in that the marginal portion is cut off by means of impact cutters or rotary cutters. It is also known to use milling machines, in which the milling cutting is moved along the fixed printed circuit board workpiece to form the latter with the desired contour. Said processes have the disadvantage that the edge portions are not finish-machined. In some of said known processes, the printed circuit board workpieces are subjected to high stresses. Besides, the machining speed is often very low and the thickness of the printed circuit boards which can be machined is limited.